The present invention relates to an oil separator used primarily in refrigerating devices and air conditioning devices for separating oil, which is carried out from the compressor along with a refrigerant gas, from the refrigerant gas and then returning this oil to the compressor, and also relates to an outdoor apparatus using such an oil separator.
FIG. 14 is an internal structural diagram of a conventional oil separator disclosed in Japanese Patent Laid-Open Publication No. Hei 8-319815.
In FIG. 14, 101 represents a shell of a substantially cylindrical shape, wherein one of open ends 101a is of a small diameter, and the other open end 101b is of a large diameter. A taper section 101c is formed at the open end 101a, and a flange section 101f which extends out in radial direction is formed at the other open end 101b. Furthermore at the open end 101b, an inlet pipe 102 is formed as an integral part of the shell 101, and an inlet port 102a is formed in the shell 101 in a tangential direction to the inner cylindrical surface of the shell 101.
103 represents an outlet pipe of a cylindrical shape with a collar section 104 formed around the middle section of the pipe, and this collar section 104 has a flange section 104f which is stuck onto the flange section 101f of the shell 101.
In this type of oil separator, a gas liquid mixture of gas and oil mist flows in from the inlet pipe 102 in a tangential direction to the inner surface of the shell 101 and circles around inside the shell 101, and centrifugal force causes the oil mist to separate and adhere to the inner surface of the shell 101, and then flow down along the inner surface and discharge from the open end 101a. Furthermore, the gas which remains after the oil mist has separated is discharged from the outlet pipe 103. Because an internal opening of the outlet pipe 103 inside the shell is larger than an external opening, the speed of the gas inside the shell 101 is reduced when being drawn into the outlet pipe 103, so that oil mist adhering to the outside wall of the outlet pipe 103 is prevented from being carried on the gas current and caught in the outlet pipe 103.
FIG. 15 is a partial longitudinal sectional view of a conventional oil separator disclosed in Japanese Patent Laid-Open Publication No. Hei 9-177529.
In FIG. 15, 201 represents a shell, which is provided with a cylindrical section 202a with an integrated flange section 202b extending outward at its top end. Furthermore, an inverted cone shaped cylinder 202c is integrally attached to the bottom edge of the cylindrical section 202a, and an oil recovery section 202d is integrally attached to the bottom opening of the inverted cone shaped cylinder 202c. In addition, an inlet pipe 203 is attached to an opening near the top end of the cylindrical section 202a. A circular lid 204 is fixed to the flange section 202b of the cylindrical section 202a. An outlet pipe 205 passes through the center of the lid 204. A non-woven fabric 206 of a predetermined shape is attached to the inside of the outlet pipe 205.
In this type of oil separator, gas incorporating oil mist flows from the inlet pipe 203 into the shell 201, and circles around within the cylindrical space formed between the cylindrical section 202a and the outlet pipe 205 extending into the cylindrical section 202a. As a result of the cyclone effect resulting from the circling gas, the oil mist in the gas, particularly with a particle diameter of 5 xcexcm or greater, collides with the inner surface of the shell 201 and condenses, and when a particle grows to a sufficiently large diameter on the inner surface, gravity causes the particle to slide down the inner surface and flow into the oil recovery section 202d. 
Furthermore, the oil mist of a smaller particle diameter, which has not separated out through collision with the inner surface of the shell 201, flows into the outlet pipe 205 together with the gas. Due to the effect of the circling motion inside the cylindrical space K, the gas does not pass straight through the outlet pipe 205, but rather moves upwards in a helical type circling motion. At this point, the velocity distribution of the gas stream is such that the velocity close to the pipe wall is large, whereas the velocity in the center is extremely small. The gas which is circling at high speed in a helical type motion around the periphery hits the non-woven fabric 206 attached to the pipe wall and is adsorbed. Repeated adsorption of these minute particles leads to an increase in the diameter of the particles adsorbed to the non-woven fabric 206, and particles which have grown sufficiently large move down the non-woven fabric 206 under the influence of gravity, drop off the bottom edge of the outlet pipe 205, and are collected in the oil recovery section 202d. 
FIG. 16 is a structural diagram showing a conventional gas liquid separator disclosed in Japanese Utility Model Laid-Open Publication No. Hei 6-60402, and FIG. 17 is a cross-sectional diagram viewed from above.
In the diagrams, a gas-liquid separator 301 includes a shell 304 formed of a combination of a cylinder 302 and a cone 303. Inlet pipes 305 for introducing a two phase flow in a tangential direction are provided on the side of the cylinder 302 of the shell 304, and this two phase flow is separated into a liquid and a vapor by the centrifugal force produced by the two phase flow circling around inside the shell 304, so that the liquid adheres to the inside wall of the shell 304 through self adhesion.
A wick is also provided on the internal wall of the shell 304 for guiding the separated liquid into the cone 303. This wick is provided with a plurality of narrow grooves 306 of 0.3 to 0.5 mm formed in a helical pattern, and the force of the circling flow and the capillary phenomenon causes the liquid to move smoothly to the cone.
In addition, in order to prevent diffusion of the two phase flow from the cylinder 302 to the cone 303, a diaphragm 307 is provided inside the shell 304 to partition the shell into two portions on the sides of the cylinder 302 and the cone 303. The diaphragm 307 is provided with small apertures 308 for connecting the cylinder 302 side with the cone 303 side to maintain a uniform pressure within the shell 304. Furthermore, a gap 309 is provided between the outer perimeter of the diaphragm 307 and the inner surface of the shell 304. A wire gauze folded in a wave like pattern is put as a coarse wick, inside the cone 303 side of the shell 304 partitioned by the diaphragm 307, and functions as a liquid collector 310 for accumulating liquid. A liquid guide pipe 311 for guiding liquid out of the shell 304 is formed at the apex of the cone 303. Furthermore, an outlet pipe 312 is formed in the center of the cylinder 302 side of the shell 304 partitioned by the diaphragm 307, so as to pass through the end plate 302a of the cylinder 302 side.
In this type of conventional oil separator and gas liquid separator, the ideal positional relationship between the outlet pipe and the inlet pipes is unclear. Therefore, in systems in which the flow rate of the refrigerant varies in accordance with high pressure and low pressure fluctuations in the refrigerating cycle caused during load fluctuations, or in systems in which the compressor controls the capacity in accordance with the load, the system is unable to deal appropriately with such a problem that though the system operates appropriately at the time when the refrigerant flow rate is large, the velocity of the circling gas inside the oil separator falls and the oil separation efficiency resulting from the cyclone effect declines at the time when the refrigerant flow rate falls. Here, the oil separation efficiency is the ratio of the volume of oil discharged from the discharge pipe per a unit of time, relative to the volume of oil flowing into the oil separator per the unit of time.
If such a configuration is adopted that the diameter of the inlet pipe is reduced at the time of low flow rate in order to alleviate this problem, the pressure loss will increase at the time when the gas velocity flowing into the shell is increased, so that the efficiency of the refrigerating cycle will decline.
Furthermore, in the case where the separated oil cannot be suitably discharged from the oil separator, the volume of oil accumulated inside the shell increases, and the accumulated oil inside the oil separator is lifted up by the gas flow inside the oil separator and flows out of the outlet pipe, producing a problem of a reduction in the oil separation efficiency.
In addition, if a diaphragm is provided as shown in FIG. 16, or an adsorbent material such as a non-woven fabric for trapping oil mist is provided in the outlet pipe as shown in FIG. 15, in order to prevent the lifting of oil within the shell, the problem of increased cost associated with the increase in the number of components arises.
The present invention aims to solve the problems described above, and an object thereof is to provide an oil separator in which fluctuations in the pressure loss and the oil separation efficiency are small even in cases where the velocity of the gas flowing into the oil separator varies or the amount of oil accumulated inside the shell varies due to a variation in the flow rate of oil into the oil separator, and moreover in which the product cost is low.
An oil separator according to the present invention is an oil separator comprising a shell having a cylindrical section and a taper section which narrows in a downward direction and which is formed as an integral part at the bottom of the aforementioned cylindrical section, an outlet pipe which is inserted through the top of the aforementioned shell so that the central axis of the outlet pipe coincides with the central axis of the shell, a discharge pipe connected to an opening provided at the bottom of the aforementioned taper section, and an inlet pipe connected tangentially to the inner surface of the aforementioned cylindrical section for introducing a gas liquid two phase flow into the aforementioned shell, characterized in that the distance between the aforementioned opening and the tip of the outlet pipe inside the shell is at least 5 times the inside diameter of the aforementioned inlet pipe.
Furthermore, an oil separator according to the present invention is an oil separator comprising a shell having a cylindrical section and a taper section which narrows in a downward direction and which is formed as an integral part at the bottom of the aforementioned cylindrical section, an outlet pipe which is inserted through the top of the aforementioned shell so that the central axis of the outlet pipe coincides with the central axis of the shell, a discharge pipe connected to an opening provided at the bottom of the aforementioned taper section, and an inlet pipe connected tangentially to the inner surface of the aforementioned cylindrical section for introducing a gas liquid two phase flow into the aforementioned shell, characterized in that the tip of the outlet pipe inside the shell is positioned below the center of the inside diameter of the inlet pipe at a distance at least 5 times the inside diameter of the inlet pipe.
Furthermore, an oil separator according to the present invention is an oil separator comprising a shell having a cylindrical section and a taper section which narrows in a downward direction and which is formed as an integral part at the bottom of the aforementioned cylindrical section, an outlet pipe which is inserted through the top of the aforementioned shell so that the central axis of the outlet pipe coincides with the central axis of the shell, a discharge pipe connected to an opening provided at the bottom of the aforementioned taper section, and an inlet pipe connected tangentially to the inner surface of the aforementioned cylindrical section for introducing a gas liquid two phase flow into the aforementioned shell, characterized in that the aforementioned inlet pipe has a straight pipe section connected to the aforementioned cylindrical section, and the length of this straight pipe section is at least 8 times the inside diameter of the inlet pipe.
Furthermore, an oil separator according to the present invention is an oil separator comprising a shell having a cylindrical section and a taper section which narrows in a downward direction and which is formed as an integral part at the bottom of the aforementioned cylindrical section, an outlet pipe which is inserted through the top of the aforementioned shell so that the central axis of the outlet pipe coincides with the central axis of the shell, a discharge pipe connected to an opening provided at the bottom of the aforementioned taper section, and an inlet pipe connected tangentially to the inner surface of the aforementioned cylindrical section for introducing a gas liquid two phase flow into the aforementioned shell, characterized in that the aforementioned inlet pipe is a bent pipe having a first straight pipe section connected to the aforementioned cylindrical section and a second straight pipe section positioned at a 90 degree angle to the first straight pipe section in the direction of the aforementioned shell.
Furthermore, an oil separator according to the present invention is an oil separator comprising a shell having a cylindrical section and a taper section which narrows in a downward direction and which is formed as an integral part at the bottom of the aforementioned cylindrical section, an outlet pipe which is inserted through the top of the aforementioned shell so that the central axis of the outlet pipe coincides with the central axis of the shell, a discharge pipe connected to an opening provided at the bottom of the aforementioned taper section, and an inlet pipe connected tangentially to the inner surface of the aforementioned cylindrical section for introducing a gas liquid two phase flow into the aforementioned shell, characterized in that the aforementioned inlet pipe is a spiral shape centered around the central axis of the aforementioned shell.
Furthermore, in each of the above configurations, the aforementioned shell has a taper section which narrows in a upward direction and which is formed on the top of the aforementioned cylinder section as an integral part of the cylindrical section.
Furthermore, in each of the above configurations, a plurality of inlet pipes are provided, and these inlet pipes are connected to the aforementioned cylindrical section at the same vertical height position with an equal spacing between the pipes.
In addition, an outdoor apparatus according to the present invention is characterized by comprising a compressor, any one of the oil separators described above with an inlet pipe connected to the compressor, a capillary tube connected to a discharge pipe of the aforementioned oil separator, a valve connected to the discharge pipe in a parallel arrangement with the capillary tube, an oil return circuit connected to the capillary tube and the valve, an accumulator connected to the oil return circuit and the compressor, a four way valve connected to an outlet pipe of the aforementioned oil separator, and a heat exchanger connected to the four way valve.
Furthermore, an outdoor apparatus according to the present invention is characterized by comprising a plurality of compressors, the aforementioned oil separator with each inlet pipe connected to one of the plurality of compressors, a capillary tube connected to the discharge pipe of the aforementioned oil separator, a valve connected to the discharge pipe in a parallel arrangement with the capillary tube, an oil return circuit connected to the capillary tube and the valve, an accumulator connected to the oil return circuit and the aforementioned plurality of compressors, a four way valve connected to an outlet pipe of the aforementioned oil separator, and a heat exchanger connected to the four way valve.
In addition, in each of the outdoor apparatuses described above, the aforementioned valve is opened only during startup of the compressor.